of the bombings, 11 minutes before the first bomb went off, a surveillance camera shows dzhokhar and tamerlan tsarnaev walking toward the boston marathon finish line with backpacks. then a surveillance camera mounted on the restaurant nearby captures crucial pieces of evidence. seven minutes before the first bombing the video which still hasn't been released shows dzhokhar walking toward the second bombing site. three minutes later he works his way into the crowd and takes his backpack off. the fbi says still photos show the backpack on the ground at his feet. when the first bomb goes off, tsarnaev remains calm as the people around him respond to the blast. he walks away without his backpack and ten second later the second bomb goes off in the spot where he left the backpack. complaint reveals that agents searched dzhokhar tsarnaev's u. mass dartmouth dorm room and they found bbs and large pyro tech. investigators found a bomb of the same brand of pressure cooker used in the bombs in the thursday night shoot-out. >> within minutes i had six of my officers, four on duty, two off duty, that are